My feeling is that the main problem with pressurising a motor is designing a good seal for the crankshaft bearing,. You will find as pressure rises, it will use more heat, and require better cooling.Ian S C

I've done away with the need for a crank shaft seal all together. The motor / generator in inside the pressurised volume. I use it to start the engine, then flick a switch over to connect it to my load.

Yes i expect the returns from increased pressure to be a lot less than theory. I can see it will show the limitations in heat exchanger surfaces. Im pretty happy the water cooled parts will be fine and stay cool. I have done some work to increase the surface area on the inside of the cylinder, ive doubled it over a smooth bore, but more would be better.

I've also allowed forma small ring between heater and cooler. At the minute its aluminium with graphite gaskets either side. But the plan is to machine this from a ceramic. I will add this at some point, the material is fairly expensive.

Good work there, that is the ideal answer. I thought perhaps you were just going to box in the current motor, with the crankshaft sticking out to take a pulley. Under ideal conditions the start motor should not need more than about one rev under power to start the motor.Ian S C

The plan is to box in the base. At the end of the crank is a gear. The motor / generator will be in a solid housing and the shaft will pass into the main housing to engage the gear. I will seal it with an o ring in the motor housing, so i can still adjust the gear ratio via different pinion gear sizes as the housing will have a degree of adjustment.

The current mounting posistion is just for now running at atmospheric. Time is fast running out on my project deadline so the results will all from atmospheric runs.

I wired it up today and sussed out the temperature data logger hardware / software. Water cooling plumbed in. So it was time to give it more of a run.

Was outside this afternoon and was a bit windy so was blowing the gas burner round a bit.